engleski

Bacterial communities in the South Adriatic dominated by SAR11

The Adriatic Sea is a semi enclosed basin of the Mediterranean with a southern part characterized by a circular, 1243 m deep South Adriatic Pit. Adriatic ecosystems are influenced by a regular water exchange with the Ionian Sea through the strait of Otranto. The purpose of this study was to characterize the temporal and spatial distribution of bacterial communities in the South Adriatic using 454 pyrosequencing of the 16S rRNA gene. Bacterial communities were characterized at two stations, one in the middle of the South Adraitic Pit and one closer to the shore, from water samples collected in October 2011 and February, March and September 2012. Taxonomic analysis of various phylogenetic groups showed a dominant depth related distribution except in February 2012 when similar communities where found at different depths. Alphaproteobacteria SAR11 clade was dominating the bacterial communities during the year. SAR11 Surface 1 clade was more abundant in the upper part while SAR11 Deep 1 clade was more specific for deeper parts of the water column in the SAP and closer to the shore. This pattern was not observed only in February 2012 when SAR11 Surface 1 clade was strongly dominating at all depths. Only in February at 800 m and 1000 m and in March at 600 m Sphingobium was dominating Alphaproteobacterial communities instead of SAR11. Cyanobacteria where characteristic for the photic zone with the highest relative abundance in October and September in both waters and with a very low abundance in February. In October 2012 Cyanobacterial communities above 10 m were dominated by Synechococcus while below 10 m Prochlorococcus was more abundant. Chloroflexi and Deferribacteres were characteristic for higher depths and their abundance was highest in October below 200 m in the SAP. In conclusion, depth related bacterial community distribution was observed in the SAP and close to the shore, with a change in structure during a year and no major spacial differences

bacteria; south adriatic pit; pyrosequencing

nije evidentirano